1. Field of the Invention
The present invention relates to adhesion promoter resin compositions, coating compositions having the adhesion promoter resin compositions, methods of coating substrates with coating compositions, and substrates coated with coating compositions.
2. Description of Related Art
Coating compositions formed from epoxy resins have been used to coat packaging and containers for foods and beverages. Although the weight of scientific evidence, as interpreted by the major global regulatory food safety agencies in the US, Canada, Europe, and Japan, shows that the levels of bisphenol A consumers are exposed to with current commercial epoxy based coatings is safe, some consumers and brand owners continue to express concern, and a coating that does not contain bisphenol A or any other endocrine disruptor is desirable.
Many coating compositions that do not contain bisphenol A or any other endocrine disruptors have not achieved the performance of epoxy based coatings and have not been successfully used on a commercial basis in food and beverage coating compositions. Some drawbacks have been delamination, flavor acceptance in beer and blush performance in pasteurized or retorted hard-to-hold beverages.
Commonly-owned U.S. Pat. No. 4,522,961 describes coating compositions having an epoxy-acrylic copolymer and up to 50 wt % of a phosphated polymer. The examples of U.S. Pat. No. '961 indicate that better results are obtained when the coating composition has a high amount of the epoxy-acrylic copolymer and a low amount of the phosphated polymer. Such results are obtained because the epoxy-acrylic copolymer has inherently good adhesion at such high levels. However, U.S. Pat. No. '961 does not explain how to obtain a coating composition that has acceptable adhesion without using an epoxy-acrylic copolymer.
There is a need to produce coating compositions that do not contain bisphenol A or are substantially free of bisphenol A. The adhesion promoter resin compositions of the invention can be used in the preparation of coating compositions suitable, inter alia, as packaging coatings for food and beverage packaging and containers.